With recent strong demands of the reduction in power consumption of image display devices, the foregoing partial drive, which is to display an image with significance only in a portion of the display area, has been carried out such as a standby-image on the screen of mobile phones. In this partial drive, a data signal line drive circuit is stopped on the occasion of the scanning of a non-display area on which no displaying is carried out, so that the reduction of power consumption is realized.
However, in the case of image display devices such as a passive matrix driving type, a simple matrix driving type, etc., it is necessary to write a voltage thereto in order to maintain the displaying, so that the data signal line drive circuit is stopped with respect to each scanning of the non-display area. In contrast, in image display devices such as a TFT active matrix type adopting the foregoing active elements, on the occasion of the partial drive, electric charges of the previous frame at the time of displaying on the entire screen are remained in pixels. To resolve this, Japanese Laid-Open Patent Application No. 11-184434/1999 (Tokukaihei 11-184434; published on Jul. 9, 1999) discloses a driving method in which an OFF voltage for non-displaying is applied to the pixels in the non-display area in the first frame period, and no voltage is applied to these pixels in the frame periods after the first frame period. In other words, in this driving method, the data signal line drive circuit is stopped except during the first frame. With this arrangement, this invention aims at reducing the frequency of charging a data signal line whose capacity is larger than that of a pixel capacitor, and reducing the power consumption.
Incidentally, there have recently been strong demands for higher resolution and displaying of moving images, and hence the mobility of the foregoing active elements is getting higher, in order to speedily write electric charges into the pixels. However, the higher the mobility of the active elements becomes, the more a leak current on the occasion of OFF-state increases. For this reason, in the foregoing arrangement of the conventional art, an unnecessary image which seems like a line defect is generated in the non-display area, since a voltage written into the pixels in the display area influences on the pixels of non-display area.